1. Field of the Invention
The present invention relates to a thermal storage method and a thermal storage apparatus of which primary object is thermal storage, and a heat source system using those. For instance, it relates to the thermal storage method, thermal storage apparatus and heat source system used for hot-water supply, heaters and heating.
2. Related Art of the Invention
As for the conventional thermal storage apparatuses, for instance, there are the ones utilizing sensible heat of water such as a hot-water storage unit attached to an electric water heater and a compression-type heat pump hot-water supply apparatus, the ones utilizing the sensible heat of a solid such as a brick used for a thermal storage fan heater, and the ones utilizing latent heat utilizing phase change of a substance, and some of them are already put into practical use (for instance, refer to Chemical Industry Council “Thermal Storage Technology—Theory and Application thereof I,” Sinzansha Sci-tech, Oct. 10, 1996, and also refer to Chemical Industry Council “Thermal Storage Technology—Theory and Application thereof II,” Sinzansha Sci-tech, Aug. 30, 2001). The disclosure of Chemical Industry Council “Thermal Storage Technology—Theory and Application thereof I,” Sinzansha Sci-tech, Oct. 10, 1996, and Chemical Industry Council “Thermal Storage Technology—Theory and Application thereof II,” Sinzansha Sci-tech, Aug. 30, 2001 are incorporated herein by reference in their entireties.
As for chemical thermal storage using a reaction including a system of decomposition or separation into composition of two or more kinds, it uses reaction heat so as to obtain thermal storage density several to ten times larger compared to methods of the thermal storage using the sensible heat and latent heat (refer to Japanese Patent Laid-Open No. 5-172481 for instance and Japanese Patent Laid-Open No. 5-118593, and also refer to Chemical Industry Council “Thermal Storage Technology—Theory and Application thereof II,” Sinzansha Sci-tech, Aug. 30, 2001). The disclosure of Japanese Patent Laid-Open No. 5-172481 and Japanese Patent Laid-Open No. 5-118593 are incorporated herein by reference in their entireties.
For instance, as for a chemical thermal storage method using an organic chemical reaction having a high thermal storage density, there is the one using a 2-propanol dehydrogenizing reaction (decomposition reaction) as shown in a chemical formula 1. Here, ΔH denotes variation in enthalpy.
[Chemical formula 1](CH3)2CHOH (l)=(CH3)2CO (g)+H2 (g) ΔH=100kJ/mol(Here, (1) denotes a liquid state, and (g) denotes a gaseous state)
As for the reaction of 2-propanol/acetone and hydrogen system, it is possible to perform thermal storage by using a rightward endothermic dehydrogenizing reaction of the chemical formula 1 and storing these products. According to the chemical formula 1, a thermal storage amount of water as a representative example of sensible-heat thermal storage is 4.2 kJ/kg, and that of sodium sulfate 10 hydrate as a representative example. of latent-heat thermal storage is 251 kJ/kg while that of the chemical thermal storage is 1,666 kJ/kg (745 kJ/kg in the case of acetone condensation).
FIG. 1 is a diagram showing temperature dependence of ΔH, TΔS and ΔG of a 2-propanol/acetone and hydrogen reaction. In a thermodynamic relational expression of a formula 3, the reaction shown in the chemical formula 1 is ΔG=0 at 150 degrees C. or so as shown in FIG. 1. To be more specific, the endothermic reaction does not progress in terms of balance at less than 150 degrees C., and progresses at temperature of 150 degrees C. or more. In general, is imposed and reaction products such as hydrogen are separated from this system so as to move the balance and thereby generate the endothermic reaction at 70 to 80 degrees C. or so.
[Formula 3]ΔG=ΔH−TΔS
T: Thermal storage temperature
ΔS: Variation in entropy
ΔG. Variation in free energy
Next, a description will be given as to the conventional thermal storage apparatus utilizing the 2-propanol/acetone and hydrogen system reaction shown in the chemical formula 1 by taking a chemical heat pump as an example.
FIG. 20 is a diagram showing the configuration of the conventional chemical heat pump listed in Japanese Patent Laid-Open No. 61-128071. The disclosure of Japanese Patent Laid-Open No. 61-128071 is incorporated herein by reference in their entireties.
In FIG. 20, reference numeral 201 denotes a dehydrogenation reaction apparatus of a shell-and-tube type heat exchange method of decomposing liquid isopropanol into gaseous acetone and hydrogen by using waste heat of about 80 degrees C. as a heat source. Reference numeral 202 denotes a distilling column of an internal multistage tray method of separating the gaseous acetone from the gaseous isopropanol accompanied by hydrogen in a gaseous substance generated in the dehydrogenation reaction apparatus 201. Reference numeral 204 denotes a hydrogenation reaction apparatus of the shell-and-tube type heat exchanger method of bringing in an unresponsive gas of the acetone and hydrogen from the distilling column 202 and generating heat at about 200 degrees C. by a hydrogenation reaction to return it to the gaseous isopropanol as a reaction product gas. Reference numeral 203 denotes a heat exchanger of an indirect contact method, provided between the distilling column 202 and the hydrogenation reaction apparatus 204, of heating the gaseous acetone and hydrogen flowing from the distilling column 202 to the hydrogenation reaction apparatus 204 with gas heat of the isopropanol gas and unresponsive acetone and hydrogen flowing from the hydrogenation reaction apparatus 204 to the distilling column 202 and increasing temperature. Reference numeral 205 denotes a steam drum. Reference numeral 206 denotes a waste heat fluid supply pipe. Reference numeral 207 denotes a waste heat fluid discharge pipe. Reference numeral 208 denotes piping. Reference numeral 209 denotes a liquid circulation pipe. Reference numeral 210 denotes a first water-supply pipe. Reference numeral 211 denotes a second water-supply pipe. Reference numeral 212 denotes a first steampipe. Reference numeral 213 denotes a second steam pipe.
And reference numeral 214 denotes a condenser of a shell-and-tube type heat exchanger method, provided on a dehydrogenation reaction side, of bringing in the gaseous acetone and hydrogen from the distilling column 202 and condensing the acetone to separate it from the hydrogen. Reference numeral 215 denotes a cooling water supply pipe to the condenser 214. Reference numeral 216 denotes the cooling water discharge pipe thereof. Reference numeral 217 denotes a flow regulating valve provided to the cooling water discharge pipe 216. Reference numeral 218 denotes a hydrogen gas line of supplying the hydrogen from the condenser 214 to a low-temperature side inlet of the heat exchanger 203. Reference numeral 219 denotes a condensate liquid storage tank. Reference numeral 220 denotes a condensate liquid line of connecting the tank 219 to the condenser 214. Reference numeral 221 denotes a separation column, provided on a hydrogenation reaction side, of bringing in the liquid acetone from the condensate liquid storage tank 219 and heating it with a reaction product substance and an unresponsive substance from a high-temperature side outlet of the heat exchanger 203 to gasify it. Reference numeral 222 denotes an acetone liquid first line connected to the tank 219. Reference numeral 223 denotes an acetone liquid second line connecting the acetone liquid first line 222 to an upper portion of the distilling column 202. Reference numeral 224 denotes an acetone liquid third line connecting the acetone liquid first line 222 to the upper portion of the separation column 221. Reference numeral 225 denotes a pump provided to the acetone liquid first line 222. Reference numeral 226 denotes the flow regulating valve provided to the acetone liquid second line 223. Reference numeral 227 denotes the flow regulating valve provided to the acetone liquid third line 224. Reference numeral 228 denotes a cooler of the shell-and-tube type heat exchanger method described later. Reference numeral 229 denotes the cooling water discharge pipe to the cooler 228. Reference numeral 230 denotes the cooling water discharge pipe thereof. Reference numeral 231 denotes a reboiler of the shell-and-tube type heat exchanger method described later. Reference numeral 232 denotes an acetone gas line connecting a top of the separation column 221 to a middle of the hydrogen gas line 218. Reference numeral 233 denotes a blower provided to the acetone gas line 232. Reference numeral 234 denotes a reaction product gas first line connected to the hydrogenation reaction apparatus 204. Reference numeral 235 denotes a reaction product gas second line connecting the line 234 to a high-temperature side inlet of the heat exchanger 203. Reference numeral 236 denotes a reaction product gas third line connecting the line 234 to the reboiler 231. Reference numeral 237 denotes a reaction product gas fourth line connecting the cooler 228 to the high-temperature side outlet of the heat exchanger 203. Reference numeral 238 denotes a reaction product gas fifth line connecting the reboiler 231 to the middle of the reaction product gas fourth line 237. Reference numeral 239 denotes the flow regulating valve provided to the reaction product gas fifth line 238. Reference numeral 240 denotes a liquid return line of supplying the condensate liquid condensed in the separation column 221 from its bottom to the center of the distilling column 202. Reference numeral 241 denotes the pump provided to the liquid return line 240. Reference numeral 242 denotes the flow regulating valve provided to the liquid return line 240. Reference numeral 243 denotes the flow regulating valve provided to the waste heat fluid discharge pipe 207. Reference numeral 244 denotes a pressure controller of detecting pressure of the distilling column 202 and controlling the valve 243. Reference-numeral 245 denotes a temperature controller of detecting a gas temperature of the hydrogen gas line 218 and controlling the valve 217. Reference numeral 246 denotes an unresponsive gas line connecting the hydrogenation reaction apparatus 204 to the low-temperature side outlet of the heat exchanger 203. Reference numeral 247 denotes the flow regulating valve provided to the unresponsive gas line 246. Reference numeral 248 denotes the pressure controller of detecting the pressure of the steam drum 205 and controlling the valve 247. Reference numeral 249 denotes the flow regulating valve provided to the first water-supply pipe 210. Reference numeral 250 denotes a liquid level controller of detecting a liquid level of the steam drum 205 and controlling the valve 249. Reference numeral 251 denotes a flow controller of inputting a detection signal from a detector 252 of detecting a flow rate of the liquid return line 240 and detecting the liquid level of the distilling column 202 to control the valve 242. Reference numeral 255 denotes the flow controller of detecting the flow rate of the acetone liquid third line 224 and controlling the valve 227. Reference numeral 254 denotes the liquid level controller of detecting the liquid level of the separation column 221 and controlling the valve 239. Reference numeral 255 denotes the liquid level controller of detecting the liquid level of the condensate liquid storage tank 219 and controlling the valve 226. Reference numeral 256 denotes a hydrogen gas holder. Reference numeral 257 denotes a hydrogen gas storage line provided branchlike from the hydrogen gas line 219 and connected to the holder 256. Reference numeral 258 denotes a compressor provided to the line 257. Reference numeral 259 denotes an opening and closing valve provided to the line 257. Reference numeral 260 denotes a hydrogen gas takeout line connecting the hydrogen gas storage line 257 between the holder 256 and the valve 259 to the hydrogen gas line 218. Reference numeral 261-denotes an acetone liquid storage tank. Reference numeral 262 denotes an acetone liquid storage line provided branchlike from the acetone liquid third line 224 and connected to the tank 261. Reference numeral 263 denotes the opening and closing valve provided to the line 262. Reference numeral 264 denotes an acetone liquid takeout line connecting the tank 261 to the line 224. Reference numeral 265 denotes the pump provided to the line 264. Reference numeral 266 denotes an isopropanol liquid storage tank. Reference numeral 267 denotes an isopropanol liquid storage line provided branchlike from a discharge side of the pump 241 of the liquid return line 240 and connected to the tank 266. Reference numeral 268 denotes the opening and closing valve provided to the line 267. Reference numeral 269 denotes an isopropanol liquid takeout line connecting the tank 266 to an intake side of the pump 241 of the liquid return line 240. Reference numeral 270 denotes the opening and closing valve provided to the line 269.
The chemical heat pump constituted as shown in FIG. 20 uses the isopropanol as a reacting substance to perform the endothermic reaction with the dehydrogenation reaction apparatus 201 by using the waste heat of about 80 degrees C. as the heat source and performs an exothermic reaction with the hydrogenation reaction apparatus 204 at about 20 degrees C.
To be more specific, a heat source fluid such as water or vapor having reached about 80 degrees C. due to factory waste heat, earth's heat or solar heat enters the dehydrogenation reaction apparatus 201 from the waste heat fluid supply pipe 206 so as to heat liquid isopropanol inside and be discharged from the waste heat fluid discharge pipe 207. A part of the liquid isopropanol heated to about 80 degrees C. in the dehydrogenation reaction apparatus 201 (boiling point of isopropanol is 82.4 degrees C. under atmospheric pressure) is decomposed into the gaseous acetone (boiling point of acetone is 56.2 degrees C. under atmospheric pressure) and gaseous hydrogen (boiling point of hydrogen is −252.7 degrees C. under atmospheric pressure), and turns to a gas-liquid mixed fluid and is led into the distilling column 202 by way of the piping 208 so that the gas rises.
Furthermore, the chemical heat pump shown in FIG. 20 has the condenser 214 of condensing the gaseous acetone and separating it from hydrogen, the separation column 221 of gasifying the condensed acetone, the hydrogen gas holder 256, the acetone liquid storage tank 261, the isopropanol liquid storage tank 266 and so on. Therefore, transport and storage of the substances between the dehydrogenation reaction side and the hydrogenation reaction side are performed in a gaseous state as to the hydrogen, and are performed in a liquid state as to the acetone and isopropanol.
To be more specific, to describe the devices, the condenser 214 brings in the gaseous acetone and hydrogen generated in the distilling column 202 and cools them to condense the acetone. The hydrogen separated here is sent to the low-temperature side inlet of the heat exchanger 203 by way of the hydrogen gas line 218. The acetone condensed in the condenser 214 leads to the condensate liquid storage tank 219 by way of the condensate liquid line 220. And it further flows in the acetone liquid first line 222 by means of the pump 225 so that a part of it is supplied to the upper portion of the distilling column 202 by way of the acetone liquid second line 225 while the other part is supplied to the upper portion of the separation column 221 by way of the acetone liquid third line 224.
In the distilling column 202, the acetone liquid having fallen from above as supplied from the acetone liquid second line 223 directly contacts the gaseous isopropanol, acetone and hydrogen generated in the dehydrogenation reaction apparatus 201 and led into the distilling column 202. The liquid acetone evaporates and joins the gaseous acetone and hydrogen, and the accompanying gaseous isopropanol gets condensed and leads to the column bottom.
The cooler 228 cools the isopropanol which is a reaction product gas and the acetone and hydrogen which are the unresponsive gases from the high-temperature side outlet of the heat exchanger 203 so that a part of the isopropanol gets condensed and the other part is supplied as a gaseous fluid to the central portion of the separation column 221.
In the separation column 221, the acetone liquid having fallen from above as supplied from the acetone liquid third line 224 directly contacts the fluid supplied from the cooler 228. The liquid acetone evaporates, and of the fluids supplied from the cooler 229, only isopropanol gets condensed and leads to the column bottom, and the others join the hydrogen of the hydrogen gas line 218 and is supplied to the low-temperature side inlet of the heat exchanger 203 by means of the blower 233.
The reboiler 231 provides to the separation column 221 a heat quantity insufficient to evaporate the entire quantity of the acetone liquid having fallen in the separation column 221. To be more specific, the reboiler 231 is provided in order to supplement and adjust the heat quantity insufficient in the separation column 221.
The pump 241 pressure-feeds the liquid isopropanol retained at the bottom of the separation column 221 to the distilling column 202.
In the case where the hydrogen generated in the condenser 214 is redundant, the hydrogen gas holder 256 closes the opening and closing valve (not shown) provided to the hydrogen gas takeout line 260, and opens the opening and closing valve 259 of the hydrogen gas storage line 257 to operate the compressor 258 so as to inject and store the redundant hydrogen. Inversely, in the case where it is insufficient, it closes the opening and closing valve 259 and stops the compressor 258, and opens the opening and closing valve of the hydrogen gas takeout line 260 so as to supply the stored hydrogen from the hydrogen gas takeout line 260 to the hydrogen gas line 218. In the case of a steady operation with no excess or deficiency of the hydrogen, the compressor 258 is stopped, and both the valves of the opening and closing valve 259 and the hydrogen gas takeout line 260 are closed.
In the case where the acetone liquid generated in the condenser 214 and stored in the condensate liquid storage tank 219 is redundant, the acetone liquid storage tank 261 opens the opening and closing valve 263, and stores the redundant portion of the acetone liquid flowing in the acetone liquid third line 224 by means of the pump 225. Inversely, in the case where it is insufficient, it closes the opening and closing valve 263, and operates the pump 265 to supply the stored acetone liquid from the acetone liquid takeout line 264 to the acetone liquid third line 224. In the case of the steady operation with no excess or deficiency of the acetone, the opening and closing valve 263 is closed and the pump 265 is stopped.
In the case where the isopropanol liquid generated in the separation column 221 is redundant, the isopropanol liquid storage tank 266 opens the opening and closing valve 268 and closes the opening and closing valve 270, and stores the redundant isopropanol liquid flowing in the liquid return line 240 by way of the isopropanol liquid storage line 267 by means of a discharge force of the pump 241. Inversely, in the case where it is insufficient, it closes the opening and closing valve 268 and opens the opening and closing valve 270 so as to have the stored isopropanol liquid absorbed into the pump 241 from the isopropanol liquid takeout line 269. In the case of the steady operation with no excess or deficiency of the isopropanol liquid, the opening and closing valves 268 and 270 are closed.
Therefore, as for the chemical heat pump shown in FIG. 20, the hydrogenation reaction apparatus 204 has the gaseous acetone and hydrogen supplied from the unresponsive gas line 246, and a predetermined hydrogenation reaction is performed. And in the case where excess or deficiency arises as to the unresponsive substances and reacting substances, an adjustment can be made as to the storage and release in the hydrogen gas holder 256, the acetone liquid storage tank 261 and the isopropanol liquid storage tank 266 respectively.
Thus, the chemical heat pump to which the isopropanol is the reacting substance comprises the condenser of bringing in and cooling the gaseous acetone and hydrogen from the distilling column and condensing the acetone to separate it from the hydrogen and the separation column of bringing in the liquid acetone generated in the condenser and heating it with the reaction product substance and unresponsive substance from the high-temperature side of the heat exchanger to gasify it. And both of the hydrogen separated by the condenser and the gaseous acetone generated in the separation column are sent to the low-temperature side inlet of the heat exchanger. Therefore, there is no interference with the heat exchange by the heat exchanger and the hydrogenation reaction by the hydrogenation reaction apparatus, and they will be performed as predetermined. In addition, it has the hydrogen gas holder of temporarily having a hydrogen gas flow in to be stored and then flow out between it and hydrogenation gas line connecting the condenser to the low-temperature side inlet of the heat exchanger, the acetone liquid tank of temporarily having the liquid acetone flow in to be stored and then flow out between it and an acetone liquid line of supplying the liquid acetone to the separation column, and the isopropanol liquid storage tank of temporarily having the liquid acetone flow in to be stored and then flow out between it and the liquid return line of supplying the condensate isopropanol from the separation column to the distilling column. Therefore, in the case where excess or deficiency arises as to the unresponsive substances and reacting substances, it is possible to store and release the hydrogen, acetone and isopropanol respectively. Thus, it is possible, in a relationship between a waste heat side and a heat use side, to store the heat in the case where the heat of a waste heat source is redundant and release the stored heat in the case where it is insufficient so as to constantly make rational use of the waste heat.
As for a hot-water storage tank used for an electric water heater and a compression-type heat pump hot-water supply apparatus, installation space thereof is a serious factor in blocking its diffusion in view of housing complexes and urban housing situation so that further miniaturization of a thermal storage tank is demanded.
However, in the case of applying a chemical thermal storage method using a system using an inorganic chemical reaction capable of operating at low temperature of a room temperature level or hydrogen absorbing alloys to a use which needs to efficiently store low-temperature heat of less than 100 degrees C. such as the above hot-water storage tank, it is not possible to store thermal energy at a sufficiently high density.
In the case of using the organic chemical reaction shown in the chemical formula 1, for instance, it is possible to obtain a relatively large thermal storage amount so as to obtain a high thermal storage density by storing hydrogen, acetone and so on. As for domestic heat storage, however, it is necessary to store heat quantity as low as possible such as less than 70 degrees C., and it is difficult to absorb and store effectively the heat of such a low temperature level by using the chemical reaction exemplified by the above chemical formula 1. To be more specific, it is necessary to have the reaction progress at further low temperature for the sake of storing the heat of a domestic hot water supply level at a high density.
In consideration of the problems of the thermal storage method, an object of the present invention is to provide the thermal storage method, thermal storage apparatus and heat source system capable of storing the heat of the domestic hot water supply level at the high density.